Electronic structure of Ge-2 and Ge-2 and thermodynamic properties of Ge-2 from all electron ab initio investigations and Knudsen effusion mass spectroscopic measurements

Irene Shim, M. Sai Baba, K.A. Gingerich

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The low-lying states of the molecule Ge-2 and of the ion Ge-2(-) have been investigated by all electron ab initio multiconfiguration self-consistent field (CASSCF) and multi-reference configuration interaction (MRCI) calculations. The relativistic corrections for the Darwin contact term and for the mass-velocity term have been determined in perturbation calculations. Treatment of the spin-orbit coupling has been included. The ground state of Ge-2 is derived as 0(g)(+)((3)Sigma(g)(-)) with equilibrium distance 2.422 Angstrom, and vibrational frequency 270 cm(-1). The spectroscopic constants of 15 excited states are presented. Thermal functions based on the theoretically determined molecular parameters were used to derive the thermodynamic properties of the Ge-2 molecule from new mass spectrometric equilibrium data. The literature value for the dissociation energy of Ge-2 has been re-evaluated. The recommended dissociation energy, D(())degrees (Ge-2), and enthalpy of formation, DeltafH(298.15)degrees(Ge-2), in Kj mol(-1) are 260.7 +/- 6.8 and 484.8 +/- 6.8, respectively.
Original languageEnglish
JournalChemical Physics
Issue number1
Pages (from-to)9-20
Publication statusPublished - 2002

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